Ultra-High-Hard Composites of TiC-TiB₂ Prepared by Combustion Synthesis under High Gravity

The large-bulk solidified TiC-TiB2 composites were prepared by combustion synthesis in high-gravity field. XRD, FESEM, SEM and EDS results showed that TiC-TiB2 composites were mainly composed of TiC matrix in which a number of fine TiB2 platelets were embedded, surrounded by the boundary regions consisting of (Cr, Ti) C0.63 carbides. The hardness, flexural strength and fracture toughness of TiC-TiB2 composites measured 28.5GPa, 750±25MPa and 6.2±0.5MPa•m1/2. High hardness of the composites benefits from the absence of the intermediate borides and the achievement of stoichiometric TiC phases due to rapid solidification, whereas the achievement of high strength benefits the refinement and homogeneity of the microstructures due to rapid separation of liquid oxides in high-gravity field and rapid coupled growth of TiC and TiB2 phases.